A new (logical) source code line.
This is used to change the value of the ruby interpreter source and line values.
There is one such node for each logical line. Logical line differs
from physical line in that a ';' can be used to make several logical
line out of a physical line and a physical line if it is in a comment
or in a string does not necessarily correspond to a physical line.
This is normally a wrapper around another more significant node.
The parser generates such a node around each separate statement.